[coverage] Conformance findings: ERRORRECOV-013

まず、tests/ 配下の coverage PR diff にある失敗しているテスト test_rate_limit_retry_count_zero_disables_retries を読み、次に OpenSession に使用されている Thrift のリトライ設定を追跡します。永続的な 429 の状況で、明示的なリトライ回数 1 によって OpenSession の呼び出しがちょうど 1 回になり、デフォルトポリシーでは引き続きリトライされ、エラーに指定された rate-limit の文言が含まれることが完了の条件です。

Summary

Surfaced by the multi-language coverage fan-out while conformance-testing these SPEC-IDs against databricks/databricks-sql-python. Each finding is committed as an expected-failure (xfail) test in the coverage PR — the test asserts the CORRECT (post-fix) behavior and stays red until THIS driver (databricks/databricks-sql-python) is fixed, then flips green as a tripwire.

Findings

• ERRORRECOV-013 [thrift]: Thrift backend ignores an explicit disable-retries retry count: _retry_stop_after_attempts_count=1 still yields 2 OpenSession attempts under a persistent 429 (the count becomes urllib3's total, which raises MaxRetryError only after the extra attempt); the kernel/SEA backend honours the same kwarg correctly
  • failing test: test_rate_limit_retry_count_zero_disables_retries (see the coverage PR diff under tests/)

Reproduce & Expected

ERRORRECOV-013 — Validate the rate-limit retry COUNT knob (the reference driver's RateLimitRetry), as distinct from the retry TIME BUDGET that ERRORRECOV-010 covers.

Expected (per the shared spec):

• [thrift] exactly 1 OpenSession call(s)
• [sea] exactly 1 CreateSession call(s)
• full assertion contract:

result:
- label: retries_disabled
  error:
    contains:
    - '429'
    - too many requests
    - rate
- label: default_policy
  error:
    contains:
    - '429'
    - too many requests
    - rate
protocol:
  thrift:
  - label: retries_disabled
    call_count:
      method: OpenSession
      expected: 1
  - label: default_policy
    call_min:
      method: OpenSession
      min: 2
  sea:
  - label: retries_disabled
    call_count:
      operation: CreateSession
      expected: 1
  - label: default_policy
    call_min:
      operation: CreateSession
      min: 2

Context

• The behavior was first fixed in a DIFFERENT driver — reference PR: https://github.com/databricks/databricks-odbc/pull/180 — which seeded the shared language-neutral spec. This issue tracks the same conformance gap in databricks/databricks-sql-python; the reference PR is for cross-referencing the intended behavior, NOT a change to this repo.
• Coverage PR carrying the reproducing xfail test(s): https://github.com/databricks/databricks-driver-test/pull/1109